The relationship between Alzheimers Disease, aging and altered calcium disposition is currently a topic of great discussion. The present project is designed to characterize alterations in free radical production, protein oxidation, enzymatic activity, protein-protein interactions and modifications in calcium buffering capacity of mitochondria. Mitochondria are a major intracellular source and sink for calcium within the neuron. Alterations in the metabolic status and transport capability of mitochondria could significantly influence the ability of the cell to regulate intracellular calcium levels. Alterations of intracellular calcium levels could result in significant dysfunction due to the critical regulation of local calcium concentrations with respect to activation of wide variety of calcium dependent enzymes. Since mitochondria are likely to function as local regulators of the cytosolic concentration of calcium on a moment to moment basis, mitochondria damage becomes a crucial determinant of the calcium homeostatic potential of a neuron. Age related changes in mitochondrial glutathione levels, mitochondrial transport of calcium and cytosolic enzymatic activity and protein-protein interaction will be determined in the first portion of this project. In the second portion, in vivo and in vitro oxidative damage to mitochondria and other components of the cell will be characterized. In the last series of experiments, the beneficial effects of chronic exposure to a free radical spin-trapping compound (PBN) will be determined. In previous studies it has been demonstrated that daily administration of PBN for a period of 14 days will significantly reduce the level of oxidized protein within the brain and return to normal the level of glutamine synthetase activity, a marker for oxidative damage to enzymes within the cell. It is hypothesized that the chronic administration of a spin-trapping compound will significantly reduce the oxidative stress to the neurons as they age and thereby, improve the survivability of the neurons. In summary, the current proposal is designed to characterize the critical role of intracellular calcium buffering capacity on protein oxidation, loss of protein-protein interaction and inability of mitochondria to buffer calcium. This loss of calcium buffering potential may be pivotable in the process of age related cellular dysfunction, not only to the normal process of aging but also in the pathological aging associated with Alzheimers Disease.